WHY NEURONS DIE - CELL-DEATH IN THE NERVOUS-SYSTEM

It is likely that humans are born with all of the nerve cells (neurons ) that will serve them throughout life, For all practical purposes, wh en our neurons die, they are lost forever. During nervous system devel opment, about one-and-a-half times the adult number of neurons are cre ated. These ''extra'' neurons are then destroyed or commit suicide. Th is process of programmed cell death occurs through a series of events termed apoptosis and is an appropriate and essential event during brai n development. Later in life, inappropriate neuronal cell death may re sult from pathological causes such as traumatic injury, environmental toxins, cardiovascular disorders, infectious agents, or genetic diseas es, In some cases, the death occurs through apoptosis, In other cases, cell death is random, irreversible, and uncontrollable; to distinguis h it from the controlled, planned cell death of apoptosis, we call thi s necrotic cell death, Understanding the difference between apoptotic and necrotic cell death is essential for designing therapies which wil l prevent or limit inappropriate cell death in the nervous system. Ana t. Rec, (NewAnat.): 253:79-90 1998. (C) 1998 Wiley-Liss, Inc.